The invention provides a power head of a vertical shaft type rock core drilling machine. The power head comprises a power head shell which is connected with a transfer case, wherein compression and decompression oil cylinders are arranged at left and right sides of the power head shell; a vertical shaft guide pipe is arranged in the power head shell in the vertical direction; the vertical shaft guide pipe is internally provided with a vertical shaft; the upper end of the vertical shaft is connected with a hydraulic clamping disc; a pressing beam is arranged between the upper side of the vertical shaft and the hydraulic clamping disc; the left and right ends of the pressing beam are downward and are connected with the compression and decompression oil cylinders; left and right guide rods are downward arranged at the front part of the pressing beam; the power head shell has a guide hole which is matched with the left and right guide rods to play the guiding role; a middle transmission section of the vertical shaft is cylindrical and a columnar surface of the middle transmission section of the vertical shaft is provided with an outer involute spline; an inner involute spline which is matched with the vertical shaft for transmission is arranged on the inner wall of the vertical shaft guide pipe; and the machining process performance of an involute spline vertical shaft is good, the guide precision is high, the drilling precision is correspondingly improved and a clamped grinding phenomenon is not generated. The power head has the advantages that the service life is greatly prolonged, the power head is suitable for large-batch production, the forming of a complete set is rapid, and the like.